Great point! I think a valuable thing to understand is that wheels and propellers are very obviously more efficient than legs and wings, respectively. There's a

Great point! I think a valuable thing to understand is that wheels and propellers are very obviously more efficient than legs and wings, respectively. There's a reason ornithopters are at most a curiosity outside of fiction (looking at you Dune!) Maple seeds are able to take advantage of the efficiency gains of revolute motion by having their entire body rotate rather than using a static body with a freely-moving prop.